I took out the uncapped wifi date deal for R249 per month,I paid their pro-rata while I was busy with the agent on the phone

I took out the uncapped wifi date deal for R249 per month,I paid their pro-rata while I was busy with the agent on the phone. Now I was debited almost R600 instead of R249. I called their useless call center and even messaged them on Facebook but still nothing is being done. I want my money I can't pay R578 for a R249 deal that's not right at all.